Optical waveguide and spot size converter using this

Abstract

An optical waveguide includes a substrate in the shape of a flat plate; lower clad that is disposed on the substrate; and a core that is disposed on the lower clad and transmits light. The optical waveguide includes a first optical waveguide and a second optical waveguide. The first optical waveguide includes a first core on the lower clad, and is disposed so as to extend along a direction in which the light travels to a first position. The second optical waveguide includes a second core on the lower clad, is disposed so as to extend along a direction in which the light travels to a second position, and has a lower relative refractive index difference than the first optical waveguide. The first optical waveguide and the second optical waveguide form, between the first position and the second position, a layer structure where the first core and the second core are disposed such that the first core is positioned a predetermined distance away from the second core in a direction perpendicular to the substrate. At least either the first optical waveguide or the second optical waveguide includes a mode coupling section and a mode conversion section. The mode coupling section includes a directional coupler to conduct the mode coupling of the first core and the second core between the first position and the second position. The mode conversion section is connected to the mode couplingsection, and has a tapered core structure to adjust the mode diameter of the first core to the mode diameter of the second core.

Description

technical field [0001] The present invention relates to an optical waveguide and a spot size converter using the optical waveguide, in particular to the shape of an optical waveguide coupled with an optical fiber and ideas about the configuration of the optical waveguide. Background technique [0002] With the advancement of communication technology in recent years, various types of developments have been made on optical circuits that are part of optical communication systems. Since planar lightwave circuits are excellent in improving functions, reducing size, and reducing costs, expectations for optical waveguide devices are rising. [0003] In an optical waveguide device, in order to couple an optical waveguide to an optical fiber in a very efficient manner, the modes of the optical waveguide need to match those of the optical fiber. Generally, the relative refractive index difference Δ of the optical waveguide is larger than that of the optical fiber, and the mode diamet...

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Problems solved by technology

[0005] However, the Δ of the optical waveguide gradually increases as the size of the optical waveguide device decreases, and according to the above method, the processing size of the optical waveguide needs to be very fine and very precise

Therefore, it becomes difficult to adjust the mode diameter to the diameter of the fiber

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